Clear and frequent communication is essential to ensure that study participants and communities are true partners in microbicide research. Effective messages are needed to explain the purpose of a study, the research process, and the results and their implications. And communication to a variety of audiences — including potential users, health care providers, men, policymakers, and the media — will be a critical part of microbicide introduction. Communication campaigns will be needed to generate demand for new products, promote adherence to microbicide regimens, convey the importance of routine HIV testing, emphasize the continued need for risk reduction through safe behavior, and create a supportive environment for microbicide use.